How HIV Hijacks The Immune System

A 3-D model of HIV peeled back to show its layers. HIV's genetic material sits inside a spherical shell (gray matrix) studded with spikes (dark gray and orange). The sphere pops open when a T cell tugs on a spike.

A 3D model of HIV pealed back to show its layers. HIV is like a jack-in-the-box. Its genetic material sits inside a spherical shell (gray matrix) studded with spikes (dark gray and orange). The sphere pops open when a T cell tugs on a spike.

On the left, one HIV spike sits on the virus's surface, ready to interact with an immune cell. When finger-like projections on T cells bind to the spike,the virus bursts open and releases its genes into the cell. Current gene therapies prevent this interaction.

HIV—red circles—have two strategies for shuttling around the immune system. It can infect T cells (yellow) directly, and it can hide out in the nooks and crannies of other immune cells (pink), waiting for a T cell to reach in and grab it. This image was obtained by electron tomography.

A 3D model of HIV pealed back to show its layers. HIV is like a jack-in-the-box. Its genetic material sits inside a spherical shell (gray matrix) studded with spikes (dark gray and orange). The sphere pops open when a T cell tugs on a spike.

One HIV spike sits on the virus's surface, ready to interact with an immune cell. When finger-like projections on T cells, such as CCR5, bind to the spike, the virus bursts open and releases its genes into the cell. Current gene therapies prevent this interaction.

Here the HIV spike--represented by the wire frame--connects with the CCR5 receptor--turquoise balls. CCR5 sits on the surface of T cells. When it engages with the HIV spike, the HIV shell pops open and release the virus's genes into the T cell. Current gene therapies protect T cells from infection by disrupting the CCR5 gene.

A 3-D model of HIV peeled back to show its layers. HIV's genetic material sits inside a spherical shell (gray matrix) studded with spikes (dark gray and orange). The sphere pops open when a T cell tugs on a spike.

On the left, one HIV spike seen on the virus' surface. When it bumps into a T cell, a finger-like projection on the cell's surface, called CCR5, pushes down on the spike. This interaction pops open the HIV and releases the infectious genes into the cell. A gene therapy could protect T cells by inactivating the CCR5 gene.

HIV--the red circles--has two strategies for shuttling around the immune system. It directly infects T cells (yellow), and it hides out on the surface of other cells (pink), waiting for a T cell to reach in and pick it up. This 3-D model is obtained from electron tomography.

Courtesy of Sriram Subramaniam and Donald BlissNIH

Originally published on July 24, 2012 12:23 pm

The road to a cure for AIDS is in sight, even if every step on the journey isn't clear yet.

One of the most promising avenues is a kind of gene therapy that would block HIV's entry into cells of the immune system. A genetic tweak could make these key cells resistant to the virus's attack.

"HIV is like a jack-in-the-box," says Sriram Subramaniam, a biophysicist at the National Cancer Institute who peers at HIV with electron microscopes.

The virus's genetic material sits inside a shell that is studded with spikes. To infect a cell, the shell has to pop open and release the virus's genes into the cell.

That's what happens when HIV bumps into T cells, the white blood cells that are the virus's prime targets.

T cells are studded with finger-like projections, including one called CCR5 that fits on HIV's spikes.

A gene therapy now being tested in people takes the CCR5 receptor out of their T cells. Without CCR5, the cells don't trigger the virus's jack-in-the-box invasion. If the virus can't get inside the cells, it can't reproduce.

A few people, mainly Caucasians, lack CCR5 because of genetic mutations. And one man who received bone marrow transplants for leukemia from a donor without CCR5 receptors has been cured of HIV/AIDS, his doctors say.

Separately, Subramaniam has found evidence that HIV hide in other places in the immune system even before it enters cells.

Using a microscopy technique to create 3-D models of cell surfaces, he and his team saw some immune cells took on flower-like shapes. HIV can hide in crevices between the large petal-like sheets.

These pools of HIV may help the virus's move around the immune system, Subramaniam tells Shots.

The virus gets a free ride as these cells move through the blood. "T cells can reach deep into these channels to pick up the HIV itself," says Subramaniam.

Copyright 2012 National Public Radio. To see more, visit http://www.npr.org/.